Why does aluminium foil spark in a microwave but not in an oven?

Ever wondered why aluminium foil sparks in microwaves but not conventional ovens? It's all about how energy is delivered.
New York Post

The hidden health hazard lurking in your office microwave — and what to do if you must reheat there

Wafts of reheated fish might seem like the most toxic landmine in the office kitchen, but there are actually bigger hazards waiting in the microwave. Experts say to beware of the office break room, ...